Specifically, the present invention relates to a device for monitoring electronic circuit units, which has at least one internal data line for forwarding internal data in the electronic circuit unit to external circuit units, and at least one data connection line for outputting the internal data from the electronic circuit unit and for inputting external data from external circuit units into the electronic circuit unit.
Electronic circuit units (also referred to as electronic components or chips) perform a specified function that is preceded by a switching-on sequence or initialization, which must be complied with exactly.
So that the electronic circuit units can perform their prespecified function, the switching-on sequence or a specific initialization mode must be complied with exactly.
Read and write access operations for memory banks, for example DDR2 (Double Data Rate 2) DRAM (Dynamic Random Access Memory) memory chips, are based on bursts. DDR2 SDRAM chips must be powered up and initialized in a predefined manner. Operating procedures other than those specified may lead to an undefined operating state.
A power-up and initialization sequence takes place until the electronic circuit unit is in an idle state. On the basis of this state, it is now possible to perform or address all of the functions of the electronic circuit unit.
Specific functions, for example test mode functions, which are essentially known only to manufacturers of the electronic circuit units (chip manufacturers) can be used to change internal voltages or to record internal voltages from outside the electronic circuit unit to be monitored.
However, internal voltages and internal signals which are used in the electronic circuit unit to be monitored can be detected only after the initialization mode or the initialization procedure has taken place, that is to say that an access operation for measuring the internal voltage is effected only after a power-up and initialization procedure has taken place.
The fact that internal voltages in the electronic circuit unit to be monitored can be detected only after the initialization mode has been run through results in the fundamental drawback that the electronic circuit unit to be monitored (to be tested) cannot be analyzed or monitored in the critical power-up phase.
In many cases, however, it is important to monitor this phase, in particular, as fully as possible, since an electronic circuit unit often cannot be initialized completely.
In a case such as this, the electronic circuit unit is then not operational or not fully operational either.